Power transmission apparatus for an automobile

ABSTRACT

Disclosed is a power transmission apparatus for an automobile comprising an engine  1,  a generator  15  driven by an output of the engine  1,  and a motor  29  driven by a generation output of the generator  15  and a discharge output of a battery  47,  wherein a clutch mechanism  23  is provided between an output shaft of the engine  1  and an output shaft of the generator  15.  In a hybrid vehicle, a loss caused by an inertia torque of the generator can be avoided.

This application is a continuation of application Ser. No. 09/576,819,filed May 24, 2000, issued Dec. 12, 2001 as U.S. Pat. No. 6,328,670;which was a continuation of application Ser. No. 09/300,519 filed Apr.28, 1999, issued Nov. 7, 2000 as U.S. Pat. No. 6,142,907.

BACKGROUND OF THE INVENTION

The present invention relates to a construction of a power train systemcomprising an internal combustion engine (hereinafter referred to as anengine), an electric power device (hereinafter referred to as a motor)and a power transmission apparatus, and particularly to a powertransmission apparatus adapted to enhance the transmission efficiency ofthe power train system.

Japanese Patent Laid-Open No. Hei 8-98322 discloses a known exampleusing a power transmission apparatus adapted to enhance the transmissionefficiency of the power train system.

In the above publication, there is described a power train constructionin which an engine and a generator are connected to each other through aspeed increasing gear, and a torque from an output shaft of thegenerator is transmitted to a motor through a clutch. In theabove-described power train construction, since the generator and themotor permit high accuracy adjustment of the number of revolutions ofthe output shaft, torque variation at the time of switching between aseries mode and a parallel mode (series mode: running by only the motorusing energy generated by the engine; parallel mode: running by theengine and the motor) caused by engagement and disengagement of theclutch can be suppressed.

It is necessary for the above-described system to synthetically controlthe engine, the motor and the generator so that an operator (a driver)may operate the engine and the motor in a high efficiency region whilesatisfying acceleration and deceleration required by an operator.Therefore, a constitution is provided in which the engine is connectedto the generator, and a torque from the output shaft of the generator istransmitted to the motor through the clutch.

With this constitution, in the case where the vehicle is intended to beaccelerated in the state in which the clutch is engaged (the parallelmode), an inertia torque of a generator rotating portion occurs, and itis necessary to correct a torque corresponding to the inertia torque bythe engine or the motor. Thus, it is impossible to avoid an increase infuel consumption due to the inertia torque.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention, inthe case where the aforementioned parallel mode operation is employedand charging of a battery is not necessary, to suppress the generationof the inertia torque thereby improving fuel economy of the vehicle.

For achieving the aforementioned object, there is provided a powertransmission apparatus for an automobile comprising an engine, agenerator driven by an output of the engine, a battery charged by ageneration output of the generator, and a motor driven by a dischargeoutput of the battery, wherein a clutch mechanism is provided between anoutput shaft of the engine and an output shaft of the generator.

Preferably, the clutch mechanism is a device which requires no energyfor engagement and disengagement when it is engaged or disengaged.

Preferably, the clutch of the clutch mechanism is a dog clutch.

Preferably, there is used a clutch mechanism using a linear actuator(e.g. a motor, a gear and a rack) for driving the dog clutch.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a constitutional view of a hybrid automobile systemaccording to one embodiment of the present invention;

FIG. 2 shows a control block diagram of FIG. 1;

FIG. 3 shows the target torque characteristics of a drive shaft of FIG.1;

FIG. 4 shows shift command characteristics of FIG. 1;

FIG. 5 shows a system constitutional view in a series mode of FIG. 1;

FIG. 6 shows a system constitutional view in a parallel mode at lowspeed of FIG. 1;

FIG. 7 shows a system constitutional view in a parallel mode at highspeed of FIG. 1;

FIG. 8 shows a time chart at the time of operation in a series mode ofFIG. 1;

FIG. 9 shows a time chart at the time of operation in a parallel mode ofFIG. 1;

FIG. 10 shows a time chart at the time of switching a shift mechanism ofFIG. 1;

FIG. 11 shows a time chart at the time of trouble of an actuator of FIG.1; and

FIG. 12 shows one example of a wobble motor applied to a linear actuatorof FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments according to the present invention will be described indetail hereinafter with reference to the drawings.

FIG. 1 shows a construction of a hybrid automobile system according toone embodiment of the present invention. In the system shown in FIG. 1,an output shaft 2 of an engine 1 has a gear 4 on the engine side for lowspeed having a meshing gear 3, a gear 6 on the engine side for highspeed having a meshing gear 5, a hub 7 and a sleeve 8 for directlyconnecting the gear 4 on the engine side for low speed or the gear 6 onthe engine side for high speed with the output shaft 2. A stopper (notshown) is provided so that the gear 4 on the engine side for low speedand the gear 6 on the engine side for high speed may not move in anaxial direction of the output shaft 2. The hub 7 is internally providedwith grooves (not shown) engaged with a plurality of grooves 9 of theoutput shaft 2. The hub 7 is movable in an axial direction of the outputshaft 2, but the movement of the hub 7 in a rotational direction of theoutput shaft 2 is limited. Thereby, the torque output from the engine 1is transmitted to the hub and the sleeve. In order to transmit thetorque from the engine 1 to the gear 4 on the engine side for low speedor the gear 6 on the engine side for high speed, it is necessary to movethe sleeve 8 in an axial direction of the output shaft 2 to directlyconnect the meshing gear 3 or 5 to the hub 7. The meshing gears 3 and 5and the hub 7 are provided with the same grooves, and the sleeve 8 isinternally provided with a groove (not shown) engaged with the sleeve 7.For movement of the sleeve 8, there is provided a linear actuatorcomprising a rack 11, a pinion 12 engaged with the rack 11, and astepping motor (1) 13. The outer peripheral portion of the sleeve 8 ismade free in the rotational direction of the output shaft 2, and a lever14 is provided which is not rotated with respect to the rotation of thesleeve 8. The clutch mechanism comprising the hub 7, the sleeve 8, themeshing gear 3 and the meshing gear 5 is called a dog clutch. Thismechanism enables the transmission of energy from a power source such asthe engine 1 to a tire 10 with high efficiency to improve fuel economy.Since the stepping motor (1) 13 can recognize the rotational angle bythe number of steps preset, a moving position of the rack 11 can bejudged. It is therefore possible to judge whether or not the gear 4 onthe engine side for low speed or the gear 6 on the engine side for highspeed is used at present, or the position is in a neutral position. Theabove-described judgement can be made by a combination of a sensor fordetecting a position of the rack and a DC motor in place of the steppingmotor.

The above-described clutch mechanism and the linear actuator are alsoapplied to the direct connection between the output shaft 2 of theengine 1 and an output shaft 16 of a generator 15. The output shaft 2 isprovided with a gear 18 for detecting the engine speed Ne of the engine1 having a meshing gear 17 rotated integrally with the output shaft 2.Further, the output shaft 16 is provided with a gear 22 for detectingthe speed Ng of the generator 15 having a meshing gear 21 and a hub 20movable along a groove 19 in the axial direction of the output shaft 16.A sleeve 23 is provided in the outer periphery of the hub 20. Further, athrust bearing 24 is provided between the output shaft 2 and the outputshaft 16 to reduce the frictional resistance caused by the contactbetween the two output shafts and prevent a deviation of the shaft. Thelinear actuator portion is composed of a lever 25, a rack 26, a pinion27 and a stepping motor (2) 28.

An output shaft 30 of a motor 29 for driving a vehicle (not shown) isprovided with a gear 31 on the motor side for low speed meshed with thegear 4 on the engine side for low speed and a gear 32 on the motor sidefor high speed meshed with the gear 6 on the engine side for high speed.The gear 31 on the motor side for low speed is also used for detectingthe speed Nm of the motor 29. Further, the output shaft 30 is providedwith a final differential gear 33 to enable the running of the vehicleby only the motor 29.

In the engine 1, the intake airflow rate is controlled by anelectronically controlled throttle 35 (comprising a throttle valve 36, adriving motor 37 and a throttle sensor 38) provided on an intakemanifold 34 so that the fuel flow rate corresponding to the intakeairflow rate is ejected from fuel injectors 39. The igniting timing isdetermined from signals of the air/fuel ratio, the engine speed and soon determined from the airflow rate and the fuel flow rate, and ignitionis made by an ignitor 40. The fuel injectors 39 include an intake portinjection system in which fuel is injected to an intake port, or adirect injection system in which fuel is injected directly into acylinder. Preferably, operating regions required by the engine (regionsdetermined by the engine torque and the engine speed) are compared toselect an engine of the system which can improve fuel economy and hasthe excellent exhaust performance.

Next, the control device for the engine 1, the generator 15 and themotor 29 will be explained with reference to FIG. 2, a control blockdiagram, FIG. 3, a target drive shaft torque characteristic, and FIG. 4,a shift command characteristic. First, into a power train control unit41 of FIG. 1 are input an accelerator pedal angle α, a brake pedal forceβ, a shift lever position Ii, a battery capacity Vb, the speed Nm of themotor 29 detected by a motor speed detector 42, the engine speed Nedetected by an engine speed detector 43, and the generator speed Ngdetected by a generator speed detector 44. In the power train unit 41,torque of the engine 1 is calculated, and transmitted to an enginecontrol unit 45 by LAN as communication means. Within the engine controlunit 45, an opening degree of a throttle valve for achieving the enginetorque, the fuel flow rate and the ignition timing are calculated, andtheir respective actuators are controlled. Further, in the power traincontrol unit 41, the torques of the motor 29 and the generator 15, andthe number of steps of the stepping motor (1) 13 and the stepping motor(2) 28 are calculated, and transmitted to the motor control unit 46 byLAN so that the actuators therefor are controlled. The motor controlunit 46 allows to charge electric power obtained from the generator 15in a battery 47 and supply power from the battery 47 to drive the motor29 and the like. Referring to FIG. 2, in the power train control unit41, first, the vehicle speed Vsp is calculated by the function f fromthe motor speed Nm in the process 48. Then, in the process 49, thetarget drive shaft torque Ttar intended by an operator is calculatedfrom the vehicle speed Vsp, the accelerator pedal angle α, the brakepedal force β, and the shift lever position Ii. In the process 50, ashift command Ss is calculated from the target drive shaft torque Ttarand the vehicle speed Vsp to select the gear 3 for low speed or the gear6 for high speed. Finally, in the process 51, torques of the actuators(an engine torque Te, a motor torque Tm and a generator torque Tg), astep number Sn1 of the stepping motor (1), and a step number Sn2 of thestepping motor (2) are calculated from the target drive shaft torqueTtar, the vehicle speed Vsp, the battery capacity Vb, the engine speedNe and the generator speed Ng, and output.

In FIG. 3, the axis of abscissa indicates the vehicle speed Vsp, and theaxis of ordinate indicates the target drive shaft torque Ttar. A portionabove a point of intersection of the two axes represents that the drivetorque is positive, while a portion below represents that the drivetorque is negative. A portion on the right hand of the point ofintersection represents a forward travel, while a portion on the lefthand represents a backward travel. The solid line indicates theaccelerator pedal angle α (%), and the diagonal line indicates the brakepedal force β. The larger % of the accelerator pedal angle α, the largerthe target drive shaft torque Ttar because an operator demands a greatacceleration feeling. In case of the backward travel, since the vehiclespeed need not be increased, the target drive shaft torque is small. Thebrake pedal force β shows a high value in the lower part in FIG. 3, itindicates that an operator demands a great deceleration. In the lowvehicle speed at which the accelerator pedal angle α is 0%, the targetdrive torque is positive to generate the torque of the motor 29 so as tosimulate the generation of the maximum torque at stall speed using atorque converter.

Next, the applied operating regions of the engine 1 and the motor 29will be explained. The mesh region is a motor driving region, and thediagonal region is an engine driving region. Normally, in a region wherethe target drive shaft torque Ttar is small at the time of the forwardtravel and the backward travel in terms of the compact and light weightof the engine 1 and the motor 2 and the improvement in fuel economyresulting from the high efficiency operation, it is necessary to driveonly the motor 1. Further, in the case where the target drive shafttorque Ttar is negative, the revival operation of the motor 1 isexecuted to make the deceleration demanded by an operator and theimprovement in fuel economy by recovery of energy compatible.

FIG. 4 shows the shift command Ss characteristics of a shift mechanismusing the dog clutch for making the operation region of the engine 1 andthe motor 29 highly efficient. In FIG. 4, the shift command Ss isdetermined by the vehicle speed Vsp and the target drive shaft torqueTtar. In the shift command Ss, the value in which the engine 1 and themotor 29 has the maximum efficiency in the overall operation region isobtained in advance by the experiment or simulation and stored in memorymeans (not shown) within the power train control unit 41.

The operation principle of the system constitution shown in FIG. 1 willbe explained with reference to FIGS. 5 to 10. FIG. 5 shows the systemconstitution in a series mode, FIG. 6 shows the system constitution in aparallel mode at the time of low speed, FIG. 7 shows the systemconstitution in a parallel mode at the time of high speed, FIG. 8 is atime chart at the time of operation in a series mode, FIG. 9 is a timechart at the time of operation in a parallel mode, and FIG. 10 is a timechart at the time of switching a shift mechanism.

In FIG. 5, the series mode termed herein is an operation in which thegenerator 15 is driven by the engine 1, and the motor 29 is driven bypower charged in the battery 47 to run the vehicle. In this case, thestepping motor (1) 13 is rotated rightward, the rack 11 is movedleftward, and the sleeve 8 is set to a neutral position. Further, thestepping motor (2) 28 is rotated rightward, the rack 26 is movedleftward, and the sleeve 23 is set to the meshing gear 17 mounted on theoutput shaft 2 of the engine 1. Thereby, the engine 1 drives only thegenerator 15 to enable charging the battery 47. Further, the generator15 can be operated also as a motor, and the engine 1 is started by thegenerator 15. Next, one example of the running of the system shown inFIG. 5 will be explained with reference to FIG. 8. In FIG. 8, the axisof abscissa indicates the time, and the axis of ordinate indicates theshift lever position Ii, the accelerator pedal angle α, the brake pedalforce β, the motor torque Tm, the vehicle speed Vsp, the batterycapacity Vb, the engine speed Ne, step number Sn1 of the stepping motor(1), step number Sn2 of the stepping motor (2), and the generator speedNg. The running conditions are the case where the vehicle starts fromits stop state, and the accelerator pedal angle α is changed duringrunning. An operator applies a brake in the state where the shift leverposition is N (neutral), and therefore, the vehicle stops. The batterycapacity is also in a state requiring no charge. When the batterycapacity exceeds 75%, the efficiency lowers, and when it is not morethan 50%, the voltage drop is great to lower discharge power. It istherefore desirable that charging of the battery 47 is executed in themesh portion shown in FIG. 8. After the shift lever position has beenmoved (a) to D (drive: forward) from N (neutral), the motor torque Tm isdetermined according to the accelerator pedal angle α. Immediately afterN to D shift (a), since the accelerator pedal angle α, is 0% and thevehicle is in a low speed, the motor torque Tm is positive by themaximum torque at stall rotation, so that the vehicle starts to run.Thereafter, the battery capacity Vb is reduced by the use of the motor29. At the time (b) when the battery capacity Vb is lower than 50%, thegenerator 15 is used as a motor to start the engine 1. Thereafter, thegenerator 15 is used as a generator and charging is executed by thetorque of the engine 1. In the case where an operator sets theaccelerator pedal angle α to 0% (c) and applies a brake (d), the revivalis executed by the motor 29 to charge the battery.

In FIG. 6, the parallel mode termed is an operation in which thegenerator 15 is driven by the engine 1, the motor 29 is driven by powercharged in the battery 47 to run the vehicle and at the same time thetorque of the engine 1 is applied to drive the vehicle. In this case,the stepping motor (1) 13 is rotated rightward, the rack 11 is movedleftward, and the sleeve 8 is set to the meshing gear 3 provided on thegear 4 on the engine side for low speed. Further, the stepping motor (2)28 is rotated rightward, the rack 26 is moved leftward, and the sleeve23 is set to the meshing gear 17 provided on the output shaft 2 of theengine 1. Thereby, the torque of the engine 1 is transmitted to the tire10 through the gear 4 on the engine side for low speed and the gear 31on the motor side for low speed. One example of the running of thesystem shown in FIG. 6 will be explained hereinafter with reference toFIG. 9. In FIG. 9, the axis of abscissa indicates the time, and the axisof ordinate indicates the shift lever position Ii, the accelerator pedalangle α, the brake pedal force β, the motor torque Tm, the engine torqueTe, the drive shaft torque To, the vehicle speed Vsp, the engine speedNe, step number Snl of the stepping motor (1), step number Sn2 of thestepping motor (2), and the generator speed Ng. The running conditionsare the case where the accelerator pedal angle α is changed duringrunning at constant vehicle speed. When the accelerator pedal angle α isgreatly applied (e), the target drive shaft torque Ttar increases.Therefore, it is necessary to increase the motor torque Tm and outputthe engine torque Te. Since at that time, the engine 1 and the generator15 are integrated, the output shaft 2 of the engine 1 is adjusted to thespeed (speed of the motor 29) of the gear 4 on the engine side for lowspeed by the generator 15, the stepping motor (2) is rotated to thepositive side (right rotation: movement leftward of the rack 11) at f,and the sleeve 8 is meshed with the meshing gear 3 of the gear 4 on theengine side for low speed. Thereby, the parallel mode is enabled byaddition of the smooth engine torque Te. When the accelerator pedalangle α lowers (g), only the engine torque Te is set to zero, andrunning is effected by only the motor torque Tm. At this time, the shiftcaused by the movement of the sleeve 8 is not carried out in terms ofreduction in shock at the time of deceleration.

FIG. 7 shows a parallel mode at the time of high speed. Here, thestepping motor (1) 13 is rotated leftward, the rack 11 is movedrightward, and the sleeve 8 is set to the meshing gear 5 provided on thegear 6 on the engine side for high speed. The stepping motor (2) 28 isrotated leftward, the rack 26 is moved rightward, and the sleeve 23 isdisengaged from the output shaft 2 of the engine 1. Thereby, the torqueof the engine 1 is transmitted to the tire 10 through the gear 6 on theengine side for high speed and the gear 32 on the motor side for highspeed. At acceleration, the generator 15 is disengaged from the outputshaft 2 and a torque corresponding to an inertia torque of the generatorcan be reduced. Therefore, it is not necessary to increase the torque ofthe engine 1 to improve fuel economy at acceleration. One example of therunning of the system shown in FIG. 7 will be explained hereinafter withreference to FIG. 10. In FIG. 10, the axis of abscissa indicates thetime, and the axis of ordinate indicates the shift command Ss, theaccelerator pedal angle α, the brake pedal force β, the motor torque Tm,the engine torque Te, the generator torque Tg, the drive shaft torqueTo, the vehicle speed Vsp, the engine speed Ne, step number Sn1 of thestepping motor (1), and step number Sn2 of the stepping motor (2). Therunning conditions are the case where the shift command Ss is changedduring running at constant accelerator pedal angle α. After the shiftcommand Ss has been changed (h), the shift is made by movement of thesleeve 8. Therefore, the engine torque Te and the generator torque Tgare increased temporaly, the step number Sn1 of the stepping motor (1)is set to negative, and the shift of the gear 6 on the engine side forhigh speed is executed. This is because of the fact that when torqueoccurs at the sleeve 8, the movement of the sleeve 8 is difficult. Sinceat the time of shift, the torque from the engine 1 lowers, the torque Tmof the motor 29 is increased disregarding the fuel cost to prevent thetorque from being lowered. The frequency of increase in the motor torqueTm is merely during the shift, not leading to an increase in fuel cost.

FIG. 11 is a time chart when an actuator is in trouble. In FIG. 11, theaxis of abscissa indicates the time, and the axis of ordinate indicatesa fail-safe flag Ff, the shift command Ss, the accelerator pedal angleα, the brake pedal force β, the motor torque Tm, the engine torque Te,the generator torque Tg, the drive shaft torque To, the vehicle speedVsp, step number Sn1 of the stepping motor (1), and step number Sn2 ofthe stepping motor (2). The fail conditions are the case where thestepping motor (1) is not actuated, and the gear 4 on the engine sidefor low speed is fixed. In the case where the fail is judged by thepower train control unit 41 (j), running by the motor 29 and thegenerator 15 should be executed to avoid a danger, and an input from theengine 1 is cutoff. Thereby, the engine torque Te is smoothly set tozero from j to k to reduce the shock, and the step number Sn2 of thestepping motor (2) is returned to zero, and the generator 15 is set tobe used as a motor. In the case where as the fail condition, thestepping motor (2) is fixed to the output shaft 16 of the generator 15as shown by the diagonal line, the engine torque Te is likewise smoothlyset from j to k to reduce the shock, and the step number Sn2 of thestepping motor (1) is returned to zero to set the shift position to aneutral point. Thereby, running only by the motor 29 results, and it ispossible to suppress the shock to impart an operator unpleasant feelingand avoid a danger.

FIG. 12 shows an example in which a wobble motor is applied to a linearactuator. In the case of the system as described above, since thefrequency of shift is small, when energy of the dog clutch in theoperation other than the shift is not present, the power consumption canbe reduced, and the fuel economy can be improved. So, a linear actuatorshown in FIG. 12 was applied. The sleeve 8 is provided with a lever 52for movement of the sleeve 8. A member 54 for supporting a ball 53 ismounted on the lever 52, the ball being constituted so as not totransmit rotation of a screw 56 to the lever 52. The screw 56 is rotatedby power supplied to a stator 55 to effect linear motion. Due to thelinear motion of the screw 56, the lever 52 and the sleeve 8 move sothat the shift or the like is executed. The linear actuator is not movedbecause the screw 56 is engaged with the thread portion of the stator 55with respect to reaction from the sleeve 8, and energy (power) when thesleeve 8 is fixed is not necessary. A motor comprising the screw 56 andthe stator 56 is called a wobble motor.

According to the present embodiment, there is provided a powertransmission apparatus for an automobile comprising a generator drivenby an output of the engine, a battery charged by generation output ofthe generator, and a motor driven by discharge output of the battery,wherein a clutch mechanism is provided between the output shaft of theengine and an output shaft of the generator whereby an occurrence ofinertial torque of the generator can be suppressed. Thereby, it is notnecessary to correct the inertial torque caused by the engine or themotor, thus enabling a considerable reduction in fuel cost at the timeof acceleration of the vehicle.

What is claimed is:
 1. A power transmission apparatus for an automobilehaving a mechanism in which a rotational force of an internal combustionengine and a rotational force of an electric motor are synthesized orselectively switched to drive a drive wheel, the rotational force ofsaid internal combustion engine or said drive wheel being convertible bya generator into electric power for being supplied to said electricmotor, comprising: a mechanism configured to disconnect said generatorfrom a rotational force transmission system comprised of said internalcombustion engine and said drive wheel; wherein the rotational forcetransmission system has a mechanism for switching a first transmissionsystem having a first speed change ratio to or from a secondtransmission system having a second speed change ratio such that, withrotation transmitted by said first transmission system, the rotationalforce transmission system is disconnected from said generator and, withrotation transmitted by said second transmission system, the rotationalforce transmission system is connected to said generator.
 2. A powertransmission apparatus for an automobile having a mechanism in which arotational force of an internal combustion engine and a rotational forceof an electric motor are synthesized or selectively switched to drive adrive wheel, the rotational force of said internal combustion engine orsaid drive wheel being convertible by a generator into electric powerfor being supplied to said electric motor, comprising: a mechanismconfigured to disconnect said generator from a rotational forcetransmission system comprised of said internal combustion engine andsaid drive wheel; wherein the rotational force transmission system has amechanism for switching a first transmission system having a first speedchange ratio, a second transmission system having a second speed changeratio and a neutral state for disconnecting the rotational forcetransmission system; such that with rotation transmitted by said firsttransmission system, the rotational force transmission system isdisconnected from said generator; and with rotation transmitted by saidsecond transmission system and rotation in said neutral state, therotational force transmission system is connected to said generator. 3.A power transmission device for an automobile according to claim 1,further comprising: means for holding at least one of a changing-overmechanism for changing over said rotational force transmission system,said mechanism for disconnecting said generator and a mechanism fordisconnecting said electric motor at a predetermined state; wherein saidholding means is operative to hold either said changing-over mechanismor said disconnecting mechanism at a predetermined state with only amechanical reaction force.
 4. A power transmission device for anautomobile according to claim 3, wherein means for holding saidmechanism at a predetermined state is a wobble motor.